Abstract: A modular window assembly constructed as a pre-assembled unit for closing an opening in a motor vehicle body is provided with a light assembly mounted in a frame assembly. In those preferred embodiments used as a backlight to close an opening in the sheet metal of a pickup truck, the light assembly may optionally be a high mount stop lamp or brakelight and/or a cargo light. The light assembly may have a housing and structure for connecting the light assembly to a power source. Numerous configurations and kinds of light assemblies may be used. The light assembly may optionally be mounted flush with an exterior surface of the frame. In certain preferred embodiments the frame assembly can have a circumferential main body segment and a halo segment unitary with the main body segment. The light assembly optionally can be mounted in the unitary halo segment. A light assembly, for example, can be used with fixed pane modular windows, single sliding pane modular windows and dual pane sliding modular windows.